U.S. patent application number 11/014389 was filed with the patent office on 2006-07-06 for self retaining set screw inserter.
This patent application is currently assigned to DePuy Spine, Inc.. Invention is credited to Sean Selover.
Application Number | 20060149291 11/014389 |
Document ID | / |
Family ID | 36641641 |
Filed Date | 2006-07-06 |
United States Patent
Application |
20060149291 |
Kind Code |
A1 |
Selover; Sean |
July 6, 2006 |
Self retaining set screw inserter
Abstract
A self retaining screw inserter for inserting, positioning and
removing a set screw of a spinal fixation system, includes an
active reverse-collet retainer. The active reverse-collet retainer
has fingers configured to move outward to engage and retain a set
screw. When engaged, the fingers flare outward to engage the set
screw.
Inventors: |
Selover; Sean; (Tiverton,
RI) |
Correspondence
Address: |
LAHIVE & COCKFIELD
28 STATE STREET
BOSTON
MA
02109
US
|
Assignee: |
DePuy Spine, Inc.
Raynham
MA
|
Family ID: |
36641641 |
Appl. No.: |
11/014389 |
Filed: |
December 15, 2004 |
Current U.S.
Class: |
606/104 |
Current CPC
Class: |
A61B 17/8888 20130101;
A61B 17/8877 20130101 |
Class at
Publication: |
606/104 |
International
Class: |
A61F 2/36 20060101
A61F002/36 |
Claims
1. A self-retaining screw inserter comprising: an active
reverse-collet retainer.
2. The self-retaining screw inserter of claim 1 wherein the active
reverse-collet retainer comprises at least two fingers configured
to retain a set screw.
3. The self-retaining screw inserter of claim 2 wherein the at
least two fingers are moved radially outward when the active
reverse-collet retainer is engaged.
4. The self-retaining screw inserter of claim 3 wherein the at
least two fingers are moved radially inward when the active
reverse-collet retainer is disengaged after being engaged.
5. The self-retaining screw inserter of claim 1 further comprising
a shaft attached to the active reverse-collet retainer.
6. The self-retaining screw inserter of claim 5 wherein the active
reverse-collet retainer can be engaged from an end of the shaft
opposite from the active reverse-collet retainer.
7. The self-retaining screw inserter of claim 6 wherein the active
reverse collet can be disengaged from the end of the shaft opposite
from the active reverse-collet retainer.
8. A self-retaining screw inserter comprising: an outer shaft
defining an axially extending passageway, the outer shaft
comprising: a distal tip comprising at least two fingers configured
to retain a set screw, and a proximal end configured to receive an
inner shaft; and an inner shaft comprising a push rod configured to
be inserted into the proximal end of the outer shaft and engage the
distal tip of the outer shaft, wherein when the push rod engages
the distal tip, the two or more fingers of the distal tip are moved
radially outward allowing the distal tip to retain a set screw.
9. The self-retaining screw inserter of claim 8, wherein the outer
and inner shafts are formed of stainless steel.
10. The self-retaining screw inserter of claim 8, wherein when the
push rod disengages the distal tip, the two or more fingers move
radially inward allowing the distal tip to release a set screw.
11. The self-retaining screw inserter of claim 8 wherein the inner
shaft further comprises a knob on the proximal end of the push
rod.
12. The self-retaining screw inserter of claim 11 wherein the
proximal end of the outer shaft further comprises internal threads
and the inner shaft further comprises threads configured to mate
with the internal threads of the proximal end of the outer
shaft.
13. The self-retaining screw inserter of claim 11 wherein engaging
the threads of the proximal end of the outer shaft with the threads
of the inner shaft causes the push rod to engage the distal tip of
the outer shaft causing the two or more fingers of the distal tip
to move radially outward allowing the distal tip to retain a set
screw.
14. The self-retaining screw inserter of claim 13 wherein
disengaging the threads of the proximal end of the outer shaft from
the threads of the knob of the inner shaft causes the push rod to
disengage the distal tip of the outer shaft causing the two or more
fingers of the distal tip to move radially inward allowing the
distal tip to release a set screw.
15. The self-retaining screw inserter of claim 8 wherein the outer
shaft has scallops on the outer surface to reduce pressure when
inserting and withdrawing the inserter percutaneously.
16. The self-retaining screw inserter of claim 8 wherein the outer
shaft has surface configurations on the outer surface to assist in
the manipulation of the screw inserter.
17. The self-retaining screw inserter of claim 8 wherein the
fingers of the distal tip are shaped in a modified Torx head
configuration.
18. A method of using a self retaining screw inserter comprising:
an outer shaft defining an axially extending passageway, the outer
shaft comprising a distal tip comprising at least two fingers
configured to retain a set screw, and a proximal end configured to
receive an inner shaft; and an inner shaft comprising a push rod
configured to be inserted into the proximal end of the outer shaft
and engage the distal tip of the outer shaft; wherein when the push
rod engages the distal tip, the two or more fingers of the distal
tip are moved radially outward allowing the distal tip to retain a
set screw, the method comprising. placing a set screw on the distal
tip of the outer shaft; and retaining the set screw by engaging the
distal tip of the outer shaft with the push rod of the inner shaft,
wherein the two or more fingers of the distal head are moved
radially outward to engage the set screw.
19. The method of claim 18 further comprising the step of placing
the set screw in a desired location.
20. The method of claim 19 further comprising the step of releasing
the set screw by disengaging the distal tip of the outer shaft with
the push rod of the inner shaft, wherein the two or more fingers of
the distal head are moved radially inward to disengage the set
screw.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to spinal fixation devices
used in orthopedic surgery. More particularly, the present
invention relates to an instrument for inserting and adjusting a
spinal implant, such as a set screw.
BACKGROUND OF THE INVENTION
[0002] Spinal fixation systems may be used in orthopedic surgery to
align, stabilize and/or fix a desired relationship between adjacent
vertebral bodies. Such systems typically include a spinal fixation
element, such as a relatively rigid fixation rod or plate, that is
coupled to adjacent vertebrae by attaching the element to various
anchoring devices, such as hooks, bolts, wires or screws. The
spinal fixation element can have a predetermined contour that has
been designed according to the properties of the target
implantation site and, once installed, the spinal fixation element
holds the vertebrae in a desired spatial relationship, either until
desired healing or spinal fusion has occurred, or for some longer
period of time.
[0003] Spinal fixation elements can be anchored to specific
portions of the vertebra. Since each vertebra varies in shape and
size, a variety of anchoring devices have been developed to
facilitate engagement of a particular portion of the bone. Pedicle
screw assemblies, for example, have a shape and size that is
configured to engage pedicle bone. Such screws typically include a
threaded shank that is adapted to be threaded into a vertebra, and
a head portion having a spinal fixation element receiving element,
which, in spinal rod applications, is usually in the form of a
U-shaped slit formed in the head for receiving the rod. In many
pedicle screws, the head is movable and preferably pivotable in all
directions, relative to the shaft. The ability to move the head
relative to the anchoring portion of the screw facilitates
alignment and seating of a rod connecting a plurality of screws
[0004] A set-screw, plug, cap or similar type of closure mechanism
is used to lock the rod into the rod-receiving portion of the
pedicle screw. In use, the shank portion of each screw is then
threaded into a vertebra, and once properly positioned, a fixation
rod is seated through the rod-receiving portion of each screw and
the rod is locked in place by tightening a cap or similar type of
closure mechanism to securely interconnect each screw and the
fixation rod. Other anchoring devices include hooks and other types
of bone screws
[0005] Set screws are typically set into location using
self-retaining screw inserters or self retaining drivers. These
generally use small springs to retain the set screw on the end of
the inserter or driver. These springs can deform or break when the
inserter or driver experiences too much torque during insertion.
Even though the inserter is just for initial insertion of a set
screw, frequently surgeons over-torque the inserter causing
premature failures. Another type of inserter uses a morse taper.
These also are subject to wear and failure when over-torqued. Thus
what is needed is a self-retaining screw inserter that does not
rely on springs or morse tapers.
SUMMARY OF THE INVENTION
[0006] The present invention provides an instrument for inserting
and adjusting a set screw that is capable of retaining a set screw
on the end of the instrument. With the set screw retained on the
end of the instrument, the set screw may be inserted in a
percutaneous fashion to capture a spinal fixation element in a
mating bone anchor. The present invention is intended to survive
excessive torques, which can be applied during the insertion of a
set screw, without the failing or lessening of the retaining
capabilities of the instrument.
[0007] In accordance with a first aspect a self-retaining screw
inserter comprises an active reverse-collet retainer. The
reverse-collet retainer is active in that a user selects when the
reverse-collet retainer will be engaged to retain a set screw.
Likewise, a user may select to disengage the reverse-collet
retainer thereby releasing a set screw.
[0008] In accordance with another aspect, a self-retaining screw
inserter comprises an outer shaft defining an axially extending
passageway and an inner shaft. The outer shaft comprises a distal
tip comprising at least two fingers configured to retain a set
screw, and a proximal end configured to receive an inner shaft. The
inner shaft comprises a push rod configured to be inserted into the
proximal end of the outer shaft and engage the distal tip of the
outer shaft, wherein when the push rod engages the distal tip, the
two or more fingers of the distal tip are moved or flared radially
outward allowing the distal tip to retain a set screw.
[0009] In accordance with another aspect, a method of using a self
retaining screw inserter comprising an outer shaft defining an
axially extending passageway, the outer shaft comprising a distal
tip comprising at least two fingers configured to retain a set
screw, and a proximal end configured to receive an inner shaft; and
an inner shaft comprising a push rod configured to be inserted into
the proximal end of the outer shaft and engage the distal tip of
the outer shaft; wherein when the push rod engages the distal tip,
the two or more fingers of the distal tip are moved radially
outward allowing the distal tip to retain a set screw, comprises
the steps of placing a set screw on the distal tip of the outer
shaft; and retaining the set screw by engaging the distal tip of
the outer shaft with the push rod of the inner shaft, wherein the
two or more fingers of the distal head are moved radially outward
to engage the set screw
[0010] In accordance with another aspect, a self-retaining screw
inserter comprises an outer shaft defining an axially extending
passageway and an inner shaft. The outer shaft comprises a distal
tip comprising at least two fingers configured to retain a set
screw, and a proximal end configured to receive an inner shaft. The
inner shaft comprises a push rod configured to be inserted into the
proximal end of the outer shaft and engage the distal tip of the
outer shaft, and a knob on the proximal end of the push rod,
wherein when the push rod engages the distal tip, the two or more
fingers of the distal tip are moved radially outward by the push
rod allowing the distal tip to retain a set screw.
[0011] In accordance with another aspect, a method of using a self
retaining screw inserter comprising an outer shaft defining an
axially extending passageway, the outer shaft comprising: a distal
tip comprising at least two fingers configured to retain a set
screw, and a proximal end having internal threads configured to
receive an inner shaft; and an inner shaft comprising a push rod
configured to be inserted into the proximal end of the outer shaft
and engage the distal tip of the outer shaft, and a knob on the
proximal end of the push rod having threads configured to engage
the inner threads of the proximal end of the outer shaft, wherein
when the thread of the knob of the inner shaft engage the threads
of the proximal end of the outer shaft, the push rod engages the
distal tip and the two or more fingers of the distal tip are moved
radially outward by the push rod allowing the distal tip to retain
a set screw; comprises the steps of placing a set screw on the
distal tip of the outer shaft; and retaining the set screw by
engaging the inner thread of the proximal end of the outers shaft
with the threads of the knob of the inner shaft wherein the distal
tip of the outer shaft is engaged by the push rod of the inner
shaft and the two or more fingers of the distal head are moved
radially outward to engage the set screw
BRIEF DESCRIPTION OF THE FIGURES
[0012] FIG. 1 is an exploded view of a self-retaining screw
inserter according to an embodiment of the invention.
[0013] FIG. 2 is a cross-sectional side view of the outer shaft of
the self-retaining screw inserter of FIG. 1.
[0014] FIG. 3 is a close-up cut-away view of the distal tip of the
outer shaft of FIG. 2.
[0015] FIG. 3A is a head-on view of a modified Torx head
configuration for the distal tip of FIG. 3.
[0016] FIG. 3B is a close-up cut away view of distal tip of FIG. 3
in an engaged state.
[0017] FIG. 4 is a block diagram flow chart of a method of using
the self-retaining screw inserter of FIG. 1
[0018] FIG. 5 is a cross-sectional side view depicting the
operation of the self-retaining screw inserter of FIG. 1.
[0019] FIG. 6 is a close-up truncated view of the inner shaft of
the self-retaining screw inserter of FIG. 1.
[0020] FIG. 7 is an assembled perspective view of a self-retaining
screw inserter according to another embodiment of the
invention.
[0021] FIG. 8 is a cross-sectional side view of the self-retaining
screw inserter of FIG. 7.
[0022] FIG. 9 is a block diagram flow chart of a method of using
the self-retaining screw inserter of FIG. 7.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The present invention will be described below relative to an
illustrative embodiment. Those skilled in the art will appreciate
that the present invention may be implemented in a number of
different applications and embodiments and is not specifically
limited in its application to the particular embodiments depicted
herein.
[0024] The present invention provides an improved self-retaining
set screw inserter for the insertion and removal of set screws used
in a spinal fixation system. The active, secure, and durable
retention provided by the present invention allows for the use of
the inserter percutaneously.
[0025] The self-retaining screw inserter of the present invention
features an active reverse- collet retainer. Using this
reverse-collet retainer, a user, such as a surgeon may actively
retain or release set screws for positioning purposes. Preferably,
the reverse-collet retainer has at least two fingers configured to
move radially outward to retain a set screw placed on the retainer
when the retainer is engaged. The reverse-collet-retainer is
usually attached on the end of a shaft for insertion into a body.
In certain embodiments a user may be able to engage or disengage
the retainer from the end of the shaft opposite the retainer. The
configuration and operation of the self-retaining screw inserter
may be better understood from the following figures and
descriptions.
[0026] FIG. 1 is an exploded view of one embodiment of a
self-retaining screw inserter 100 for percutaneous placement of set
screws. The screw inserter 10 comprises an outer shaft 20 and an
inner shaft 40. The outer shaft 20 defines an axially extending
passageway. The outer shaft 20 comprises a distal tip 60 and a
proximal end 80. The inner shaft comprises a push rod 50 configured
to be inserted into the proximal end 80 of the outer shaft 20 and
engage the distal tip 60 of the outer shaft 20. In certain
embodiments the inner shaft 40 further comprises a knob 70 on the
proximal end of the push rod 50 providing additional control of the
screw inserter.
[0027] FIG. 2 depicts a cross-sectional side view of the outer
shaft 20. The outer shaft 20 defines an axially extending
passageway 30 configured to receive the inner shaft. The outer
shaft has a distal tip 60 and a proximal end 80. The proximal end
80 is configured to receive the inner shaft. The push rod of the
inner shaft is inserted into the passageway 30 through the proximal
end 80. In certain embodiments, the proximal end 80 has threads 82
on the inner surface of the passageway 30 configured to mate with
threads on the inner shaft.
[0028] The outer shaft 20 is preferably made of stainless steel or
other surgical grade materials. In certain embodiments, the outer
shaft 20 has surface features on the outer surface to assist in
manipulation of the screw inserter. For example, portions of the
outer surface may be provided with grips 22. In some embodiments,
the outer shaft 20 has scallops 24 on the outer surface to reduce
pressure build up when inserting or removing the screw inserter
percutaneously. Other embodiments will be apparent to one skilled
in the art given the benefit of this disclosure.
[0029] FIG. 3 is a close-up cut-away view of one embodiment of a
distal tip 60 of the outer shaft 20. In this embodiment, the distal
tip is functioning as a reverse-collet retainer of the screw
inserter. The distal tip 60 comprises at least two fingers 62. In
certain embodiments there may be more than two fingers 62. The
fingers 62 of distal tip 60 are shaped so as to engage a set screw.
Examples of suitable shapes include, but are not limited to, Torx
head, modified Torx head, hex head, Philips head, or the like. An
example of a modified Torx head 64 can be seen in FIG. 3A. The
modified Torx head 64 features a cylinder 66 with six lobes 68
equally spaced around the diameter of the cylinder 66. Other
implementation will be apparent to one skilled in the art given the
benefit of this disclosure.
[0030] Referring now to FIG. 3B, the distal tip 60 is configured
such that when the push rod 50 of the inner shaft 40 is inserted
into the passageway 30 of the outer shaft 20 the push rod 50
engages the distal tip 60. The distal tip 60 is smaller in diameter
than the rest of the outer shaft 20 so when the push rod 50 engages
the distal tip 60, the fingers 62 are moved or flared radially
outward allowing the fingers 62 to engage a set screw 120.
[0031] A flow chart 123 depicting one embodiment of the process of
using the self-retaining screw inserter of the present invention
can be seen in FIG. 4. The first step 125 is placing a set screw on
the distal tip 60 of outer shaft 20. The next step 126 is retaining
the set screw by engaging the distal tip 60 with the push rod 50 of
the inner shaft 40. This causes the fingers 62 of the distal tip 60
to move or extend radially outward and engage the set screw thereby
securing the set screw 120 on the distal tip 60. Optionally, the
set screw may then be placed in a desired location, step 127. In
optional step 128, the set screw may then be released from the
distal tip 60 by disengaging the push rod 50 from the distal tip 60
wherein the fingers 62 move or retract radial inward disengaging
the set screw. Using this method set screws may be both inserted
and removed percutaneously. Other uses or implementations will be
apparent to ones skilled in the art given the benefit of this
disclosure.
[0032] An example of the operation of one embodiment can be seen in
FIG. 5. As shown here, the push rod 50 of the inner shaft travels
down the passageway 30 toward the distal tip 60 in the direction
indicated by arrow 100. The circumference of the outer shaft 20
decreases at the distal tip 60, so when the end of the push rod 50
engages the distal tip 60, the push rod moves or flares the fingers
62 of the distal tip 60 radially outward. The fingers 62 move
radially outward as indicated by arrows 110 and engage the set
screw 120 placed on the distal tip 60. The set screw 120 is thus
retained on the distal tip 60 allowing a user to insert the set
screw 120 percutaneously into the proper location without the fear
of losing the set screw 120. The active interference used to secure
the set screw 120 in this manner is more durable and resistant to
torque forces that may be applied by a user on the screw
inserter.
[0033] Inversely, once the set screw 120 is in a desired position,
the set screw 100 may be released from the distal tip 60 by
disengaging the push rod 50 from the distal tip 60. Here, the push
rod 50 travels thru the passageway 30 in the direction opposite of
arrow 100. Once the push rod 50 disengages from the distal tip 60,
the fingers 62 move or retract radially inward in the direction
opposite arrows 110 thereby disengaging the set screw 120.
[0034] FIG. 6 is a close-up truncated view of one embodiment of an
inner shaft 40. In this embodiment the inner shaft 40 features a
push rod 50 and a knob 70. The push rod 50 is of the size and shape
to slide along the passage way 30 of the outer shaft 20 so as to
engage the distal tip 60 of the outer shaft 20. In certain
embodiments, the tip 52 of the push rod is rounded so as to assist
in the moving or flaring of the fingers 62 of the distal tip 60.
The knob 70 is located on the proximal end of the push rod 50
opposite of the tip 52 of the push rod 50. The knob is preferably
of a diameter greater than the diameter of the rest of the inner
shaft 40 and may have surface configurations to assist in the
manipulation of the inner shaft 40. Preferably, the inner shaft is
made out of stainless steel or some other surgical grade material.
Other implementations will be apparent to one skilled in the art
given the benefit of this disclosure.
[0035] In certain embodiments, the inner shaft has threads 74 at
the base of the knob at the proximal end of the push rod 50
configured to mate with threads 82 on the inner surface of the
passageway 30 located at the proximal end 80 of the outer shaft 20.
The threads 82 on the inner surface of the passageway 30 and the
threads 74 at the base of the knob 70 allows the inner shaft 40 to
be screwed into the outer shaft 20. In such embodiments, the
greater diameter of the knob 70 provides a mechanical advantage
when screwing or unscrewing the inner shaft 40.
[0036] FIG. 7 is a perspective view of one embodiment of a
self-retaining screw inserter 10 wherein the inner shaft 40 has
been screwed into the outer shaft 20. In this particular
configuration, the screwing and unscrewing of the inner shaft 40
also controls the engaging and disengaging of the distal tip 60 by
the push rod 50 and thus the retention and release of a set screw
120. This functionality can be seen in more detail in FIG. 8.
[0037] FIG. 8 is a cross sectional view of one embodiment of the
self-retaining screw inserter 10 wherein the inner shaft 40 is
screwed into the outer shaft 20. Here the push rod 50 is inserted
into the passageway 30 so as to be able to engage the distal tip 60
of the outer shaft 20. The mating threads 74 and 82 control the
depth of insertion of the push rod 50. In this embodiment, the
threads 74 and 82 are configured so that turning the knob 70
clockwise, as indicated by arrow 130, screws in the inner shaft 40
(not shown in Figures) so that the push rod 50 engages the distal
tip 60 to secure or retain a set screw 120. Turning the knob
counter- clockwise, as indicated by arrow 135, disengages the push
rod 50 from the distal tip 60.
[0038] FIG. 9 is a flow chart 140 depicting a method of use of the
self-retaining screw inserter of FIG. 8. First a set screw 120 is
placed on the distal tip 60, step 141. Then, the set screw 120 is
secured or retained by engaging the threads 74 and 82, step 142. In
this embodiment, the threads 74 and 82 are engaged by turning the
knob 70 clockwise. Once the set screw 120 is retained, the set
screw 120 may be placed in a desired location, step 143. Once the
set screw 120 has been placed, the set screw 120 may be released by
disengaging the threads 74 and 82, step 144. In this embodiment,
the threads 74 and 82 may be disengaged by turning the knob 70
counter-clockwise. Using this method set screws may be both
inserted and removed percutaneously. Other uses or implementations
will be apparent to ones skilled in the art given the benefit of
this disclosure.
[0039] Having the inner shaft 40 screw into the outer shaft 20
allows for constant and controlled active interference to be used
to secure the set screw 120. Securing the set screw 120 in this
manner is more durable and resistant to torque forces that may be
applied by a user on the screw inserter. Another advantage is that
the self retaining screw inserter 10 of the present invention can
be disassembled into the component parts for easy cleaning.
[0040] Although, the previous examples have focused on a use of a
threaded interface to engage and disengage the distal tip 60 with
the push rod 50, other interfaces are possible. For example,
ratchet, crank, or plunger interfaces may also be used. Other
implementations and embodiments will be apparent to one skilled in
the art given the benefit of this disclosure.
[0041] The present invention has been described relative to an
illustrative embodiment. Since certain changes may be made in the
above constructions without departing from the scope of the
invention, it is intended that all matter contained in the above
description or shown in the accompanying drawings be interpreted as
illustrative and not in a limiting sense. For example, one skilled
in the art will recognize that the instrument of the illustrative
embodiment of the invention is not limited to use in percutaneous
insertion and removal.
[0042] It is also to be understood that the following claims are to
cover all generic and specific features of the invention described
herein, and all statements of the scope of the invention which, as
a matter of language, might be said to fall therebetween.
* * * * *